Many conventional laundry machines used a complex mechanism which adapted a constant speed motor, e.g., one which runs at 1800 RPM, to the comparatively slow back-and-forth motion of an agitator during a wash cycle. The same mechanism adapted the motor to a unidirectional spin cycle during which a tub rotated, alone or together with the agitator, at a speed which may have been on the order of 600 RPM. In general, the physical dimensions of the motor required for such machines, as well as the dimensions of a transmission for coupling the motor to the machine, may be large and may necessitate that the motor be positioned a considerable distance out of line with the axis of the drive shaft of the laundry machine. This distance was sufficiently large to accommodate an intermediate belt transmission, as well as whatever gearing was required to step down the speed of the motor. Further, a transmission clutch was provided to uncouple the machine from the motor whenever the agitator reverses direction during the back-and-forth motion of the latter.
The above-outlined mechanical arrangement may be unbalanced so that special measures may be necessary to restore the balance of the machine. Further, because of severe demands made on such machine, particularly on the transmission during a reversal of direction, at least some of such machines may have had a relatively short life. It is believed that the above discussed factors might find expression in high initial cost of such machines, as well as in high maintenance costs and the necessity for frequent replacement of component parts of such machines.
The transmission for the unidirectional motor required to meet the demands of such a laundry machine consequently may have a relatively large moment of inertia. Additionally, the gear transmission ratios required by the relatively high torque requirements, particularly during agitator reversal, may have further aggravated this condition. Also, the requirement for dissipating energy whenever the agitator reversed directions during the wash cycle may have produced inefficiencies. It is believed that the greater the inertia of the system, the lower is the efficiency of system operation. Thus, the initial cost of a motor of the size required for a conventional laundry machine, as well as the cost of operation of such a motor, may be high.
Finally, the range of operations of conventional laundry machines is believed to be, by necessity, limited. To provide such machines with the capability of handling a larger number of different laundry conditions, such as may be presented by a variety of present day fabrics and wash loads, is believed to materially increase the complexity of the transmission as well as the overall cost of the machine. Thus, the capability of such conventional laundry machines may represent a compromise between different expected laundry conditions, modified by cost and mechanical considerations. It is believed that this capability, selected at the manufacturing site and once determined, may be changed only with difficulty and at great expense. For practical purposes, it is believed that no changes were possible once the machine leaves the factory.